Effects of high temperature at flowering stage on the related physiological characteristics of functional leaves of rice were studied using indica rice varieties－Shuhui 527 and Texianzhan 25 as samples,which had significant differences in high temperature stability of photosynthesis.The results showed that under heat stress,Shuhui 527 with high temperature tolerance of photosynthesis presented small decreasing ranges of net photosynthetic rate and seed setting rate,large increasing range of proline cumulative level in leaves and significantly lower membrane injury rate.In addition,the thermal stability at 50.0℃ of large subunit of Rubisco (Lsu),small subunit of Rubisco (Ssu) and total protein content in Rubisco-extracting solution of flag leaves was high in Shuhui 527.Between Lsu and Ssu,the stability of Ssu was more sensitive to changes in temperature.The thermal stability of Ssu could provide a reference for studies on the identification,evaluation and mechanism of high temperature tolerance of rice at flowering stage.